The invention relates to an automation plant that reduces the power consumed by plant components in the event of a production stoppage and the method and apparatus that implements that reduced power consumption.
Automation plants can provide fully-automated or partially-automated production processes. For example, motor vehicles are produced using plant components such as robots, conveyor belts, and painting stations. When these components cannot be attended by personnel during a planned lunch break or overnight, for example, it may be desirable for these plant components to rest during the operation of the production processes. During such a production stoppage, it is advantageous for the plant components assume an energy-saving “sleep” mode in which their power requirements or power consumption is reduced.
The standards association PROFIBUS & PROFINET International (PI) has developed a standardized data interface PROFIenergy for this purpose, which is based on the PROFINET standard. With this interface, the energy demand of automation devices can be reduced by switching to energy-saving modes via a PROFINET network.
At present, PROFIenergy devices can only switch to states favoring energy saving during an individual stoppage time. The individual stoppage time, which specifies the duration of the production stoppage, is transmitted by a central control apparatus. Each device receives this stoppage time and then decides automatically, in a predefined manner, which energy-saving state (referred to as energy-saving mode) the device will change into. Then, the device transmits a wake time back to the central control apparatus, which is referred to as the PROFINET state controller (PSC). The wake time is the time at which the device needs to receive a command to wake up again in order to be operation-ready again at the end of the stoppage.
In this case, it is not possible for the central control apparatus to define the state into which the device will switch. A device in an automation plant, or a general plant component, changes automatically into a target state when specific preconditions are met. The target state is selected by the plant component depending on the stoppage time data it has received, i.e. a specific target state is assumed when the received stoppage time data specify an expected stoppage time. For example, if the stoppage time is between five minutes and one hour, a different target state can be assumed than for a stoppage time which is within a time period range of from one hour to twelve hours.
A further important precondition for assuming a specific target state consists in that at least one other plant component has a respective predetermined expected operating state. A first plant component, for example a conveyor belt, cannot stop easily when the first plant component is used to transport workpieces away from another plant component, for example a bottling plant. If the conveyor belt were to simply stop, the bottles would back up in the part of bottling plant that is still in operation. Thus, a plant component may not switch into the lowest-power target state for a production stoppage if another plant component does not have the specified operating state that is necessary for this target state.
Switching plant components centrally via a central control apparatus so that the control apparatus directly sets the target states of all of the plant components, wherein the control apparatus uses an overall model of the plant, that is formed from individual state models of each of the plant components. One disadvantage of this is that control commands for setting the target state need to be transmitted from the central control apparatus to each plant component. In some bus systems for controlling plant components, such a direct control is not possible. Plant components that have a PROFIenergy device are an example of this.